Following are the TCP/IP Application protocols:
1.DHCP:

DHCP Dynamic Host Configuration Protocol is defined by RFC’s 2131
and 2132.DHCP is Dynamic Host Configuration
Protocol (DHCP) allows IP addresses to
be allocated to hosts on an as-needed basis.DHCP lets a host
‘borrow’ an IP address from a pool of IP addresses; when the
address is no longer required it is recycled and made available for
use by other host. DHCP also allows a host to retrieve a
verity of configuration information.

DCHP depends on UDP to carry packets between the client and server
tasks.

2. DNS

The DNS (Domain Name System) provides ondemand dynamic
translation between human-readable names (like www.mydoamin.com)
and the numeric addresses actually used by IP (like
192.169.10.28). The basics of DNS operation are defined in RFC’s
1034, 1101, 1876, 1982 and 2065.

A very widely-used implementation of DNS called BIND
(Berkeley Internet Name Domain)
DNS uses both UDP and TCP. It used UDP to carry simple queries and
responses but depends on TCP to guarantee the correct and orderly
delivery of large amounts of bulk data (eg zone configurations) across the network.

3. FTP

File Transfer Protocol (FTP) provides a mechanism for transfering data
files between various systems. In addition to the fundamental PUT and GET
operations, FTP provides a small number of file management and
user authentication facilities. FTP uses port 21

FTP depends on TCP to guarantee the correct and orderly delivery
of data across the network.

4. HTTP

Hyper Text Transfer Protocol (HTTP) is the protocol used to publish
Web pages across an internet. HTTP depends on TCP to guarantee the
correct and orderly delivery of data across the network.

5. IMAP

Interactive Mail Access Protocol (IMAP) allows clients to
manipulate email messages and mailboxes that reside on some server
machine. The current version of IMAP is Version 4, IMAP is more powerful
and more complex than the other widely-used mail-reading protocol
POP.

6. NFS

Network File System (NFS) allows files stored on one machine (the
“server”) to be accessed by other machines (the “clients”) as
though the files were actually present on the client systems. NFS
is defined in terms of a Remote Procedure Call (RPC) abstraction
which in turn formats its packets according to a
processor-independent eXternal Data Representation (XDR).

NFS is most often used over UDP. UDP does not guarantee packet delivery or ordering, so
when NFS runs over UDP the RPC implementation must provide its own
guarantees of correctness.

7. NNTP

Network News Transfer Protocol (NNTP) is used to propagate netnews
postings (including Usenet postings) between systems.

8. NTP

Network Time Protocol (NTP) is used to synchronise time-of-day
clocks between various computer systems. The current version of
NTP is Version 3, defined in RFC 1305.

9. POP

Post Office Protocol (POP) allows clients to read and remove email
from a mailbox that resides on some server machine. The current
version of POP is Version 3, usually referred to as POP3. POP uses port 110

10. Rlogin

Remote Login (rlogin) provides a network terminal or “remote
login” capability. Rlogin is similar to Telnet but it adds a
couple of features that make it a little more convenient than
Telnet.

11. Rsh

Remote Shell (rsh) is an r-command that provides for remote
execution of arbitrary commands. It allows you to run a command on
a server without having to actually log in on the server. More
importantly it allows you to feed data to the remote command and
retrieve the command’s output without having to stage the data
through temporary files on the server.

12. SMTP

Simple Mail Transfer Protocol (SMTP) is used to deliver email from
one system to another. The port used by SMTP is 25.
13. SNMP

Simple Network Management Protocol (SNMP) provides a means of
monitoring and managing systems over a network. SNMP defines a
method of sending queries (the GET and GET-NEXT primitives) and
commands (the SET primitive) from a management station client to
an agent server running on the target system, and collecting
responses and unsolicited event notifications.

14. Ssh

Secure Shell (ssh) provides remote login and execution features
similar to those of the rsh and rlogin r-commands, but ssh
encrypts the data that is exchanged over the network. Encryption
can protect sensitive information, and it is not uncommon for
security-conscious administrators to disable plain rsh and telnet
services in favour of ssh.

The SSH protocol used by the ssh command has also been used to
build a secure file transfer application which can be used as an
alternative to FTP for sensitive data.

15. Telnet

Telnet provides a network terminal or “remote login” capability.
The Telnet server accepts data from the telnet client and forwards
them to the operating system in such a way that the received
characters are treated as though they had been typed at a terminal
keyboard. Responses generated by the server operating system are
passed back to the Telnet client for display.

16. X Window System

The X Window System allows client programs running on one machine to control the graphic
display, keyboard and mouse of some other machine or of a
dedicated X display terminal.

enjoy…..:)